Apparatus and method for doctor blade replacement in a flexographic press

Abstract: Apparatus and method for flexographic printing wherein a holder (24) equipped with upper and lower doctor blades (25,26) is installed in a generally C-shaped subframe (22) adjacent an anilox roll (21) in the press.

Description: BACKGROUND AND SUMMARY OF INVENTION : This invention relates to an apparatus and method for doctor blade replacement in a flexographic press and, more particularly, to a fountain embodying a movable holder for the blades. Conventionally, doctor blades are provided to define the upper and lower ends of a fountain associated with an ink transfer roll -- such as an anilox roll. Illustrative of the basic structure is that shown in co-owned Patent 5,125,341. When it is desired to replace the doctor blades, a labor-intensive situation arises. Bolts have to be loosened and then retightened in order to clamp the doctor blades and if the operation is not carefully handled, a wave will be introduced into the blade. This is avoided by the instant invention which provides a doctor blade holder which is movably mounted on a sub-frame of the press. The sub-frame of the press is part of the basic fountain structure and is located immediately adjacent the anilox roll. The sub-frame has portions for clamping the doctor blade in place on the holder and bearing against the anilox roll. The invention makes it possible to equip the movable holder with the blades at either the press or at a location remote from the press -- but in any event, quickly install the blades thereby avoiding the laborious operations of the past. Other objects and advantages of the invention may be seen in the details of the ensuing specification. BRIEF DESCRIPTION OF DRAWING : The invention is described in conjunction with illustrative embodiments in the accompanying drawing, in which -- FIG. 1 is a perspective view, somewhat simplified, of a portion of a flexographic press; FIG. 2 is a side elevational view of certain of the elements of FIG. 1 as they would be disposed during "inking" of the anilox roll; FIG. 3 is a fragmentary perspective view of the apparatus of FIG. 2; FIG. 4 is a view similar to FIG. 2 but with the subframe pivoted away from the anilox roll preparatory to doctor blade replacement; FIG. 5 is a view similar to FIG. 4 but with the doctor blades unclamped for ease of replacement; FIG. 6 is a fragmentary perspective view of the apparatus of FIG. 4; FIG. 7 is a fragmentary side elevational view of a modified version of the invention featuring a removable holder; FIG. 8 is a sectional view taken along the sight line 8-8 applied to FIG. 7; FIG. 9 is a view similar to FIG. 8 but showing the parts in a different operating condition; FIG. 10 is a side elevational view, partially schematic, of a flexographic press equipped with another modified cartridge of the invention; and FIG. 11 is a fragmentary perspective view of the cartridge portion of FIG. 10. DETAILED DESCRIPTION : In the illustration given and with reference first to FIG. 1, the numeral 20 designates generally a fragment of the frame of the flexographic press. A similar fragment is seen in FIGS. 3 and 6. Other details of the frame are omitted for ease of presentation but additional details can be seen in co-owned Patent 5,012,736. The frame 20 rotatably supports an anilox roll generally designated 21 which can be considered an ink transfer roll of the type described in greater detail in the above-mentioned 5,012,736 patent. Movably mounted on the frame for coaction with the anilox roll 21 is a subframe generally designated 22 and which is seen to be essentially C-shaped in side elevation. Still referring to FIG. 1, it is seen that the subframe 22 carries fluid pressure cylinder means 23. These cylinder means in turn carry the blade-mounting holder 24. The holder 24 is equipped with an upper doctor blade 25 and lower doctor blade 26. These blades, along with end seals 27 (only one seen at the left of FIG. 1), holder 24 and anilox roll 21 define an ink chamber 28 (see FIG. 2). In normal operation, ink is contained in ink pail 29 and is delivered through supply line 30 by motorized pump 31. The ink enters a lower port 32 in the holder 24 and the excess exits from an upper port (not shown) through the return line 33 to the pail 29. FIG. 2 shows the orientation of the just-described elements during "inking", i.e., printing. At that time, the doctor blades 25, 26 are firmly clamped to the holder by the subframe 22. More particularly, the ends of the subframe adjacent the anilox roll 21 are equipped with a top clamp bracket 34 and a bottom clamp bracket 35 -- see the right and central portions of FIG. 5. These brackets extend the length of the blades -- see for example, the bracket 35 in FIG. 6. A plurality of cylinders 23 are provided along the bracket length for uniform clamping pressure. For blade replacement, the subframe 22 is pivotally mounted on the press frame as at 36 and the pivoted "away" position is seen in FIGS. 4-6. Then the holder is withdrawn from the brackets 34, 35 by the cylinder means 23 -- see FIG. 4. The pivot axis 36 is located on the frame 20 so that both the edge of the lower doctor blade 26 and the part of the bracket 35 closest to the anilox roll 21 will clear the roll and without the need for translating the subframe 22. DOCTOR BLADE CHANGEOVER This sequence is started with the doctor chamber inked up at the end of a run, and the following steps performed: 1. Remove ink from doctor chamber by draining through supply side hole line 30. 2. Pivot the doctor blade subframe 22 to FIG. 4 position to expose chamber. This is accomplished by backing off the upper thumb screws 37 and manually pivoting the subframe against a stop provided by the frame at 38 (see FIG. 6). There, the pivot handle is designated 39 and is seen abutting the part 38 of the frame. 3. Unclamp the doctor blades by retracting air cylinder means 23 -- compare FIGS. 4 and 5. 4. Remove the used blades. 5. Wipe the remaining ink off of the anilox roll 21 and doctoring system, i.e., the holder 24, and seals 27, etc. 6. Replace the end seals 27 if needed. 7. Place new steel blades against magnets in the doctor blade holder. The magnets can be best seen in FIG. 10. In lieu of ferrous material blades-- as where plastic blades are used -- a seating recess or shoulder can be provided. 8. Clamp the blades in place with air cylinder 23. 9. Pivot doctor blade chamber back to run position and lock in place with the thumb screws 37. 10. The chamber 28 is then filled with ink and the drive for the anilox roll is started. Any excess ink on the roll is caught in the ink pan 40 -- see FIG. 2. The features/benefits of the invention are: 1. Time Saving -- the system pneumatically clamps and unclamps blades without the use of any tools and fasteners -- with approximately ten minutes saved per blade change. 2. Operator friendly -- the blade holder 24 stays in the press requiring only the handling of the blades and the end seals. 3. Safer system -- Spent blades can be removed prior to chamber washup. 4. Compatibility -- Interchanges with previous doctor blade holders with minimal changes. 5. Ease of Cleanup -- Shallow chamber 28 with drain system greatly reduces amount of ink in the chamber prior to cleanup. STRUCTURAL DETAILS These are now described first with reference to FIGS. 3 and 6. Each of these fragmentary perspective views is generally in the direction of the arrow A as applied to FIG. 1. So, in FIG. 3, the hose 30 is readily seen. So also is the handle 39 and cylinder means 23. In FIG. 6, the same three elements are designated, viz., 23, 30 and 39. Also seen clearly in FIG. 6 is the locking pin 41. This is the pin held in place by thumb screw 37 -- compare FIGS. 2 and 4. Referring again to FIG. 6, there is seen a slot 41a provided in the frame 20 which receives the pin 41 when the fountain is in the inking or printing mode. The pins 41 (one at each end) are carried by an adapter bar 42 -- see FIGS. 4 and 5. The bar 42 is slidably mounted on the subframe 22 and carries the holder 24 and the cylinder means 23. The piston rod 43 of the cylinder means 23 is attached to the bight portion 44 of the subframe 22 -- still comparing the right portions of FIGS. 4 and 5. EMBODIMENT OF FIGS. 7-9 Here like numerals are applied to similar elements but with the addition of 100. In FIGS. 8 and 9 the numerals 121 designates an anilox roll. A holder 124 is provided which has doctor blades 125 and 126 held on by magnets 145, 146 (see FIG. 9). The essential difference of this embodiment from that of FIGS. 1-6 is in the provision of a different subframe generally designated 122. However, as before, the subframe 122 and the holder 124 make up the fountain and the subframe 122 is again generally C-shaped. Physically supporting the holder 124 is an L-shaped bracket 147. The bracket 147 is slidably supported on rods 148 which constitute the lower legs of the C-shaped subframe 122 (see also FIG. 7). The rods 148 are rigidly fixed in the subframe 122 and, more particularly to the bight portion 149 of the generally C-shaped subframe 122. Pivotally mounted on the upper end of bight portion 149 is clamp member 134 -- see the extreme right of FIG. 9. Completing the C-shape is the bottom clamp member 135 mounted on rods 148. Like their counterparts in the embodiment of FIGS. 1-6, the members 134 and 135 clamp the doctor blades 125, 126 against the holder 124 so as to define chamber 128 (see FIG. 8). As can be seen in FIG. 7 at the left hand end, the bracket 147 is equipped with an end bore 150 which provides journal 151. A similar arrangement is provided at the right hand end (not shown) so as to rotatably support the overall fountain assembly on the machine frame (not shown). Once the holder 124 is desired to be replaced, the subframe 122 is retracted away from the anilox roll 121. This can be appreciated from a consideration of FIG. 9. This differs from the showing in FIG. 8 where the fountain is in operational position with the doctor blades 125, 126 bearing against the anilox roll 121. To proceed from the disposition of elements in FIG. 8 to that of FIG. 9, we both retract and rotate the holder 124. Rotation occurs about the axis 151a of the journals 151 -- see the lower center of FIG. 8. For this purpose, we connect the ends of the L-shaped bracket 147 to a suitable retraction/rotation means such as a stepping motor driving a screw actuator as seen in co-owned Patent No. 5,184,556. Alternatively, the retraction/rotation means may be in the nature of a pressure fluid cylinder, ball and screw arrangement, etc. so as to retract the ends of L-shaped bracket 147 and also rotate the same to the condition depicted in FIG. 9. Either simultaneously with the foregoing movement or shortly thereafter, the pancake cylinder 123 is energized to unclamp the holder 124. For that purpose, the cylinder 123 is rigidly mounted on the bight portion 149. The piston rod 150 of the cylinder 123 extends through the portion 149 and is coupled to the L-shaped bracket 147. As the piston rod is retracted into the air cylinder, the bight portion 149 moves toward the L-shaped bracket 147. This unclamps the lower blade 126 from the angled surface of the member 135 (see the upper left center of FIG. 9). For unclamping the blade 125 from the clamping surface on the member 134, the member 134 is pivoted by the withdrawing action of the piston rod of the cylinder 123. More particularly, the member 134 is pivotally mounted as at 151 at the upper end of the bight portion 149. As the piston rod 150 is retracted (going from the FIG. 8 showing to that of FIG. 9), the bight portion 149 moves to the left and the number 134 bears against and pivots on a mushroom-shaped button 152. This unclamps the upper blade 125. The member 134 is urged back into clamping position by the torsion spring 154 -- so that when fluid pressure is removed from the cylinder 123, the spacing 153 moves the member 134 back to its FIG. 8 position. This occurs by virtue of the torsion spring 153 being fixed at its lower end as at 153a and bears against a post 153b on member 134 at its upper end. EMBODIMENT OF FIGS. 10-11 Again, the frame 220 supports an anilox roll generally designated 221. Movably mounted on the frame for coaction with the anilox roll 221 is a subframe generally designated 222 and which is seen to include two portions or members 254 and 255. These members are pivotally interconnected at 256 and the member 255 can be pivoted to the position 255' shown in dotted line. This is advantageously achieved through a pressure fluid cylinder 223 which is mounted on a clevis fixed to the member 254. The piston rod 257 of the pressure fluid cylinder is seen to be equipped at its work end with an arm 258 rigidly connected to the upper member 255. Retraction of the rod 257 pivots the upper member 255 to the 255' position and effectively unclamps the holder 224. It will be noted that each of the members 254, 255 is generally L-shaped so as to provide parts for clamping the upper doctor blade 225 against an angled clamp surface 258 provided as part of an arm 259 which in turn is provided as part of the holder generally designated 224. Thus, the holder 224 and subframe 222 make up a fountain F. In similar fashion, the lower member 254 clamps the lower doctor blade 226 against the surface 260 provided on the holder 224. More particularly, the holder 224 is C or channel shaped having the arms 259, 261 connected by a bight portion 262. Completing the closing of the fountain are end seals as at 227 in FIG. 11. OPERATION When the holder 224 is installed as seen in FIG. 10, liquid to be taken up by the transfer roll 221 is introduced via the conduit 263 into an inlet port in the member 254 and through an aligned port in the holder 224. The member is recessed so as to accommodate the installation of an O-ring 264. In similar fashion, another O-ring is disposed about the outlet passage 265 in the member 254 which is aligned with the conduit 266. This results in a liquid level as at 267 in the ink chamber 228. The excess liquid, i.e., ink is returned for recirculation. With ink in the fountain F, the cavities in the anilox roll can be filled under the control of the upper doctor blade 225 -- assuming the rotation of the anilox roll to be in the direction of the arrow applied thereto. With reverse rotation, the doctoring is provided by the blade 226. When holder replacement is indicated -- worn doctor blades, change of liquid, etc., the fountain chamber 228 is drained and the cylinders 223 actuated to pivot the member 255 to the dotted line position 255'. The member 254 is moved relative to the frame 220 to space the fountain F from the anilox roll 221. A suitable mechanism for this can be seen in co-owned Patent No. 5,184,556. This permits the holder 224 to be withdrawn from its mounting. Then, at a site convenient to but generally remote from the flexographic press, the operator can install new doctor blades 225, 226. These are mounted against the bearing surfaces on the holder 224 and because they are normally made of ferrous material may be advantageously held in place temporarily by use of magnets 245, 246.

Claims: A fountain for a flexographic press having a frame (2) equipped with an ink transfer roll, (21, 121, 221) a subframe (22, 122, 222) mounted on said frame adjacent said roll, a holder (24, 124, 224) movably mounted on said subframe, said holder being equipped with upper and lower doctor blades (25, 26; 125, 126; 225, 226) engaging said roll and end seals (27, 227) defining with said roll a liquid chamber, and ink inlet (32, 263) and outlet (33, 266) means in said holder, said subframe having portions (34, 35; 134, 135, 254, 255) clamping said doctor blades to said holder. The fountain of claim 1 in which said holder has upper (258) and lower (260) blade supporting surfaces, means (245, 246) associated with each surface for temporarily holding said blades on said surfaces. The fountain of claim 2 in which said holding means includes magnetic means, said doctor blades being constructed of ferrous material. The fountain of claim 1 in which said subframe is generally C-shaped and equipped with a fluid pressure cylinder means (23, 123, 223) operatively coupled to said holder to unclamp said blades. The fountain of claim 1 in which pivot means (36, 151) interconnect said subframe (22, 122) with said frame (20). The fountain of claim 1 in which said subframe includes a pair (134, 149; 254, 255) of pivotally interconnected subframe members. The fountain of claim 6 in which one (134) of said subframe members is equipped with rod means, and an L-shaped bracket (147) slidably mounted on said rod means. A method for doctor blade replacement in a fountain for a flexographic press according to claim 1, comprising the steps of providing a frame equipped with an ink transfer roll, a subframe movably mounted on said frame adjacent said roll, a holder movably mounted on said subframe, said holder being equipped with upper and lower doctor blades engaging said roll and end seals defining with said roll a liquid chamber, and ink inlet and outlet means in said holder, said subframe having portions clamping said doctor blades to said holder, moving said subframe away front said ink transfer roll and moving said holder relative to said subframe to unclamp said blades. The method of claim 8 in which said steps include providing said clamping portions of a length substantially the length of said doctor blades, and applying clamping pressure at longitudinally spaced areas of said clamping portions to substantially uniformly clamp said blades. The method of claim 9 in which said steps include providing said holder with means for temporarily supporting said blades until said subframe clamping portions are brought into clamping engagement with said blades.

Inventors: EHLERS DENNIS W, HERTEL JAMES E, ZEMAN DALE E, EHLERS, DENNIS W., HERTEL, JAMES E., ZEMAN, DALE E.
Applicants: PAPER CONVERTING MACHINE CO, PAPER CONVERTING MACHINE COMPANY
Application year: 1994
Main classification: B41F31
IPC codes: B41F31